Soot sensor system

ABSTRACT

A soot sensor system and a method of sensing soot in a vehicle soot sensor system. The soot sensor system and method includes providing a soot sensor having at least one trace of conductive material in a continuous loop on a surface of a substrate, applying an alternating current (AC) input voltage to the at least one trace of conductive material to establish an AC sense current through the at least one trace of conductive material, and generating, using a peak detector, a peak detector output voltage representative of a peak value of the AC sense current and of an amount of soot accumulated on the soot sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/198,972 filed Jun. 30, 2016, now U.S. Publication No. US2017-0023461,which is a continuation of U.S. patent application Ser. No. 13/481,723filed May 25, 2012, now U.S. Pat. No. 9,389,163 issued Jul. 12, 2016,which claims the benefit of U.S. Provisional Patent Application Ser. No.61/490,310, filed May 26, 2011, the entire disclosures of which are allhereby incorporated herein by reference.

FIELD

The present disclosure relates generally to a soot sensor, and, moreparticularly, to a sensor system for detecting soot in an exhaust gasflow.

BACKGROUND

Soot sensors may be used in engine emissions applications, e.g. foron-board diagnostics (OBD). A sensor of this type may be used to detectand measure particulate matter build-up, e.g. soot concentration, in anengine exhaust gas. In diesel engines in particular, it is desirable tohave the lowest possible soot particle concentration when exhaust gas isreleased into the environment. To monitor the operating status of theinternal combustion engine, it is expedient for this purpose to positiona soot sensor in the exhaust system associated with the internalcombustion engine. The soot sensor may be positioned upstream ordownstream from a diesel particulate filter (DPF). If it is positioneddownstream from the DPF, function monitoring of the DPF may also beperformed using the soot sensor. When the DPF fails, the soot sensor maydetect excessive soot in engine exhaust and alert the vehicle enginecontrol unit (ECU).

Soot sensors may be relatively simple resistive devices. FIG. 1 is aschematic top view of one known configuration of a soot sensor having anon-board heater element, and FIG. 2 is a schematic bottom view of thesoot sensor of FIG. 1. The sensor 100 may include a non-conductivesubstrate 102 defining a first surface 104 and a second surface 106opposite the first surface 104. A sense element 108 is formed on thefirst surface 104 of the substrate 102, and includes a conductivematerial defining a first electrode 110 and a separate second electrode112. The conductive material may be a precious metal selected towithstand high temperatures, and the first 110 and second 112 electrodesmay be electrically separate from each other to establish an opencircuit therebetween.

As shown, the first and second electrodes 110, 112 may be configuredwith inter-digitized “fingers” that maximize a perimeter between thefirst and second electrodes 110, 112. The first electrode 110 defines afirst set of fingers 114 and the second electrode 112 defines a separatesecond set of fingers 116. In operation, when soot (not shown) fromexhaust lands on the sensing element 108, carbon in the sootelectrically connects the first and second electrodes 110, 112,effectively lowering the resistance therebetween. The resistance betweenthe electrodes is measured as an indication of the amount of sootpresent.

FIG. 3 is an enlarged sectional view of the soot sensor of FIGS. 1 and 2taken along line 3-3. As shown in FIGS. 2 and 3, in some applications,the sensor 100 will also have an on-board heater element 118 implementedon the second surface 106 of the substrate 102. The on-board heaterelement 118 is configured to heat the soot sensor 100 through resistiveheating. For example, it may be desirable to clean off soot that hascollected on the first and/or second surfaces 104, 106 of the substrate102. The on-board heater element 118, which may include a platinum tracewith a known resistance, may be activated, heating the sensor element108 to a relatively high temperature, e.g. 650° C., thereby causing anyaccumulated soot particles to incinerate.

A soot sensor of the type described above is susceptible to breakdownunder the conditions existing in the exhaust system. The electrodes aredirectly subjected to exhaust gas flow, wherein certain exhaustmaterials may lead to corrosion of the electrodes and/or contaminationof the sensor surface, which may have an interfering effect on sootaccumulation measurement. Additionally, the sense element of currentsoot sensors lacks diagnostic functions capable of sensing a break inthe sense element traces. Moreover, on-board heaters included in currentsoot sensors have difficulty reaching high temperatures required tosufficiently incinerate accumulated soot during high flow conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the claimed subject matter will be apparentfrom the following detailed description of embodiments consistenttherewith, which description should be considered with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic top view of a soot sensor;

FIG. 2 is a schematic bottom view of the soot sensor of FIG. 1;

FIG. 3 is an enlarged sectional view of the soot sensor of FIGS. 1 and 2taken along line 3-3;

FIG. 4 is a schematic top view of a soot sensor consistent with thepresent disclosure;

FIG. 5A is a sectional view of a portion of the soot sensor of FIG. 4taken along line 5-5 consistent with the present disclosure;

FIG. 5B is a sectional view of a portion of the soot sensor of FIG. 4taken along line 5-5 according to another embodiment consistent with thepresent disclosure;

FIG. 6 is an enlarged view of the portion of the soot sensor of FIG. 5B;

FIG. 7 is a schematic top view of another embodiment of a soot sensorconsistent with the present disclosure;

FIG. 8A is an enlarged view of a portion of the soot sensor of FIG. 7;

FIG. 8B is an enlarged view of a portion of the soot sensor of FIG. 7according to another embodiment consistent with the present disclosure;

FIG. 8C is an enlarged view of the portion of the soot sensor of FIG. 7according to another embodiment consistent with the present disclosure;

FIG. 9 is a perspective view of a soot sensor tip consistent with thepresent disclosure;

FIG. 10 is an enlarged perspective sectional view of the soot sensor tipof FIG. 9 taken along line 10-10;

FIG. 11 is a block diagram of one exemplary embodiment of a soot sensorsystem consistent with the present disclosure;

FIG. 12 is a schematic top view of the soot sensor of FIG. 7 including apassivation layer;

FIG. 13 is a schematic top view of another embodiment of a soot sensorconsistent with the present disclosure;

FIG. 14 is an enlarged view of a portion of the soot sensor of FIG. 13;

FIG. 15 is a schematic top view of the soot sensor of FIG. 13 in a sootsensing mode;

FIG. 16 is a schematic top view of the soot sensor of FIG. 13 in aregeneration mode;

FIGS. 17A-17D are schematic top views and associated circuitry of thesoot sensor of FIG. 13 in first and second regeneration modes;

FIG. 18 is a perspective sectional view of a soot sensor assemblyconsistent with the present disclosure;

FIGS. 19A-19B are perspective views of embodiments of the soot sensorassembly of FIG. 18;

FIG. 19C is an enlarged perspective view of a portion of the soot sensorassembly of FIG. 18;

FIG. 20 is a perspective exploded view of another soot sensor assemblyconsistent with the present disclosure;

FIG. 21 is a perspective view of the soot sensor assembly of FIG. 20 inan assembled state;

FIG. 22A is a sectional view of the soot sensor assembly of FIG. 21taken along lines A-A;

FIG. 22B is a section view of the soot sensor assembly of FIG. 21 takenalong lines B-B;

FIGS. 23A-23B are perspective and sectional views of one embodiment of aportion of the soot sensor assembly of FIG. 20;

FIGS. 24A-24B are perspective and sectional views of another embodimentof a portion of the soot sensor assembly of FIG. 20;

FIG. 25 is a schematic view of circuitry coupled to the soot sensor ofFIG. 13;

FIG. 26 is a block diagram of a signal processing system coupled to thesoot sensor of FIG. 13;

FIG. 27 is a schematic view of the signal protection circuitry of FIG.26;

FIG. 28 is a plot of output voltage vs. resistance associated with anexemplary soot sensor consistent with the present disclosure;

FIG. 29 includes plots of output voltage vs. time associated with anexemplary soot sensor consistent with the present disclosure;

FIG. 30A is a schematic view of circuitry associated with an exemplarysoot sensor consistent with the present disclosure;

FIG. 30B is a schematic view of circuitry associated with an exemplarysoot sensor consistent with the present disclosure;

FIG. 31 is a plot of resistance vs. time associated with the circuitryof FIGS. 30A-30B;

FIG. 32 is a plot of supply wattage vs. air flow rate associated with anexemplary soot sensor consistent with the present disclosure;

FIGS. 33A-33D are plots of supply voltage vs. time associated with anexemplary soot sensor consistent with the present disclosure;

FIG. 34 is a plot of resistance vs. time associated with an exemplarysoot sensor consistent with the present disclosure;

FIG. 35 is a plot of soot accumulation vs. time correlating to the plotof FIG. 34; and

FIG. 36 is a plot of sensor response vs. time associated with anexemplary soot sensor consistent with the present disclosure.

DETAILED DESCRIPTION

The present disclosure is generally directed to soot sensors and a sootsensor system for detecting soot particles. In general, a soot sensorsystem consistent with the present disclosure includes a substratedefining a first surface and a second surface opposing the firstsurface. At least one element having at least one continuous loop ofconductive material is disposed on the first surface of the substrate.The at least one element is configured to operate in a first mode tosense accumulation of soot on at least said first surface of saidsubstrate and to operate in a second mode to remove accumulated soot onat least said first surface of said substrate. First and secondelectrical contacts are disposed at opposite ends of the at least oneelement. Circuitry is electrically coupled to the first and secondelectrical contacts and configured to determine an amount of sootaccumulated on the first surface of the substrate and the element and tocontrol heating of the element in response to soot accumulation.

A soot sensor and/or soot sensor system consistent with the presentdisclosure may be configured to be positioned in an exhaust system of amotor vehicle having a diesel engine. Additionally, a soot sensor and/orsoot sensor system may be configured for use in the field of householdtechnology in an oil heating system, for example, it being provided withan appropriately designed support depending on the application. For usein an exhaust system of a motor vehicle, a soot sensor system consistentwith the present disclosure may be configured to detect sootaccumulation from exhaust gas flow. Additionally, the soot sensor systemmay be coupled to and configured to communicate with an onboarddiagnostics system of a vehicle. Additionally, the soot sensor may bepositioned downstream from a diesel particulate filter (DPF) of a motorvehicle having a diesel engine, wherein the sensor may be configured tomonitor the performance of the DPF.

Referring to FIG. 4, an embodiment of a soot sensor consistent with thepresent disclosure is schematically depicted. The soot sensor 400includes a substrate 402, e.g. constructed from a dielectric ornon-conductive material, defining a first surface 404 (e.g. a topsurface, as shown in FIG. 5A) and a second surface 406 (e.g. a bottomsurface, as shown in FIG. 5A) opposing the first surface 404. The sootsensor 400 includes a sensor element 408 formed on the first surface 404of the substrate 402. The sensor element 408 includes at least onecontinuous loop 410 of conductive material disposed on the substrate402. The loop 410 may take any regular and/or irregular geometric shape,e.g. serpentine, spiral, rectangular, circular, etc.

In the illustrated exemplary embodiment, the loop 410 is arranged in aserpentine configuration including a first set of a plurality ofundulations 412 and a plurality of gaps G1 and G2 defined within andbetween each of the plurality of undulations 412. In the illustratedembodiment, the portions of the loop 410 including turns 411 adjacentthe side 413 of the sensor are separated by gaps G1 and the portions ofthe loop 410 including turns 415 adjacent the side 417 of the sensor areseparated by gaps G2, and the gaps G1 are wider than the gaps G2. Theterm “serpentine” as used herein refers to a configuration includingturns of any shape, e.g. arcuate as show in FIG. 4, square, combinationsof arcuate and square etc. and also includes turns separated by gaps ofuniform and/or differing sizes.

The sensor element 408 further includes first and second electricalcontacts 414, 416 at opposite ends of the loop 410. The first and secondelectrical contacts 414, 416 may be configured for coupling to circuitryfor providing current through the loop 410. In the illustratedembodiment, an input current I_(sense) may be provided at the firstelectrical contact 414 (or second electrical 416 contact).

The value of I_(sense) may be representative of the amount of sootdisposed on the sensor 400. In the illustrated embodiment, for example,soot particles 428 are shown as accumulated on the first surface 404 ofthe substrate 402, including on the sensor element 408. As soot 428builds up on the sensor element, the resistance of the loop 410 changes,which changes the value of I_(sense). The value of I_(sense) is thusrepresentative of the amount of soot accumulated on the sensor.

The sensor element 400 further include a heater element 418 formed onthe first surface 404 of the substrate 402. The heater element 418includes at least one continuous loop 420 of conductive materialdisposed on the substrate 402. The loop 420 may take any regular and/orirregular geometric shape, e.g. serpentine, spiral, rectangular,circular, etc, and may be positioned adjacent the sensor element loop410 in at least a portion of its length.

In the illustrated exemplary embodiment, the loop 420 is arranged in aserpentine configuration including a second set of a plurality ofundulations 422 complementary to and interweaving with the first set ofplurality of undulations 412. The heater element 418 further includesfirst and second electrical contacts 424, 426 at opposite ends of theloop 420. The first and second electrical contacts 424, 426 may beconfigured for coupling to circuitry for providing current through theloop 420. In the illustrated embodiment, an input current I_(heater) maybe provided at the first electrical contact 424 (or second electrical426 contact). In one embodiment, for example, when a threshold amount ofsoot 428 accumulates on the sensor element 408, e.g. as determined byreaching a threshold value of I_(sense), the heater current I_(heater)may be applied to cause the heater element 418 to heat and at leastpartially remove, e.g. incinerate, the soot 428, therebycleaning/regenerating the sensor 400 for continued use.

The sensor element 408 may include electrically conductive materials ormetals, such as, gold, platinum, osmium, rhodium, iridium, ruthenium,aluminum, titanium, zirconium, and the like, as well as, oxides, alloys,and combinations including at least one of the foregoing metals. Theheater element 418 may include various materials. For example, materialsmay include platinum, gold, palladium, and the like and/or alloys,oxides, and combinations thereof. The substrate 402 may include anon-conductive and/or electrically insulating materials. Materials mayinclude oxides, including, but not limited to, alumina, zirconia,yttria, lanthanum oxide, silica, and/or combinations including at leastone of the foregoing, or any like material capable of inhibitingelectrical communication and providing structural integrity and/orphysical protection. Additionally, the soot sensor 400 may include thickfilm and/or thin film constructions.

FIG. 5A is a sectional view of a portion of the soot sensor 400 of FIG.4 taken along line 5-5 consistent with one embodiment of the presentdisclosure. In the illustrated embodiment, soot particles 428 areaccumulated on at least the sensor element 408. In particular, whenexposed to exhaust gas flow, the soot particles 428 may accumulatewithin at least one of the plurality of gaps G1 and/or G2 defined withinand between each of the plurality of undulations 412 of the loop 410 ofthe sensor element 408. When the sensor element 408 is free of any sootparticles, the electrical circuit of the sensor element 408 createdbetween the first and second electrical contacts 414, 416 has a firstresistance. When soot particles 428 accumulate on the sensor element408, and, in particular, within at least one of the plurality of gaps G1and/or G2, wherein the soot particle 428 makes contact with the loop410, the resistance between the first and second electrical contacts414, 416 may change. Resistance may increase as more soot particles 428collect and accumulate. The heater element 418 may be activated when itis desired to have accumulated soot particles 428 removed from the sootsensor 408. The heater element 418 may be configured to reach atemperature at which soot particles 428 are incinerated.

FIG. 5B is a sectional view of a portion of the soot sensor of FIG. 4taken along line 5-5 according to another embodiment consistent with thepresent disclosure and FIG. 6 is an enlarged view of a portion of thesoot sensor of FIG. 5B. In one embodiment, a protective layer 532 isformed over the first surface 404 of the substrate 402 and covers atleast a portion of the undulations 412, 422 of the sensor and heaterelements 408, 418, respectively. The protective layer 532 may beconfigured to insulate at least a portion of the undulations 412 of thesensor element 408 from exhaust gas flow. The protective layer 532further defines a plurality of channels 534 corresponding to and alignedwith the plurality of gaps G1 defined by the undulations 412 of sensorelement 408.

Referring to FIG. 6, each of the plurality of channels 534 exposes atleast a portion of the sensor element, e.g. edges 636 of the undulations412, to exhaust gas flow and the soot particles 428. In the illustratedembodiment, each of the plurality of channels 534 are sized and/orshaped to allow soot particles 428 to accumulate within at least one ofthe plurality of channels 534 and the corresponding gap G1, such thatsoot particles 428 make contact with at least a portion of the exposedsensor element 408 conductive material, e.g. edges 636 of theundulations 412.

FIG. 7 is a schematic top view of another embodiment of a soot sensorconsistent with the present disclosure and FIG. 8A is an enlarged viewof a portion of the soot sensor of FIG. 7. This embodiment is similar tothe embodiment of FIG. 4, and like components have been assigned likereference numerals in the seven hundreds rather than the four hundreds.The soot sensor 700 includes a substrate 702 defining a first surface704. A sensor element 708 and a heater element 718 are formed on thefirst surface 704. The sensor and heater elements 708, 718 each includeat least one continuous loop of conductive material 710, 720,respectively, disposed on the substrate 702. Similar to the embodimentof FIG. 4, the loops 710, 720 may be arranged in a serpentineconfiguration including first 712 and second 722 sets of undulations.Referring to FIG. 8A, the first 712 and second 722 sets undulationsfurther define first 828 and second 830 subsets of undulations,respectively. A plurality of gaps 832 are defined within and betweeneach of the first 828 and second 830 subsets of plurality ofundulations.

The sensor element 708 further includes first 714 and second 716electrical contacts at opposite ends of the loop 710. The first andsecond electrical contacts 714, 716 may be configured for coupling tocircuitry for providing current through the loop 710. In the illustratedembodiment, an input current I_(sense) may be provided at the firstelectrical contact 714 (or second electrical 716 contact). Similarly,the heater element 718 further includes first 724 and second 726electrical contacts at opposite ends of the loop 720. The first andsecond electrical contacts 724, 726 may be configured for coupling tocircuitry for providing current through the loop 720. In the illustratedembodiment, an input current I_(heater) may be provided at the firstelectrical contact 724 (or second electrical 726 contact).

In the illustrated embodiment, the sensor and heater elements 708, 718may be configured to be operated separately and independently from oneanother as described above regarding the embodiment of FIG. 4.Additionally, the soot sensor 700 may further include a switch S1coupled to the first 724 and second 716 electrical contacts of theheater 718 and sensor 708 elements, respectively, for selectivelycoupling and decoupling the contacts 724, 716. When the switch S1 isopen, the sense current I_(sense) is determined by the resistance of theassociated with the loop 710 of conductive material between contacts 714and 716 and varies with soot particles deposited on the loop 710,thereby allowing the sensor element to sense soot particles. When theswitch S1 is closed, loops 710 and 720 are electrically coupled inseries establishing a single continuous loop of conductive materialbetween the contacts 714 and 726. The current I_(sense) may then passthrough both the sensor 708 and heater 718 elements to allow both thesensor 708 and heater 718 elements to act as a single heater element.

FIG. 8B is an enlarged view of a portion of the soot sensor of FIG. 7according to another embodiment consistent with the present disclosure.In the illustrated embodiment, the sensor and heater elements 708, 718include continuous loops 810, 820 of conductive material disposed on thefirst surface 704. The loops 810, 820 are arranged in a serpentineconfiguration including first and second sets of a plurality ofundulations 812, 822. The first and second sets of plurality ofundulations 812, 822 further define first and second subsets ofplurality of undulations 834, 836, respectively. A plurality of gaps 838are defined within and between each of the first and second subsets ofplurality of undulations 834, 836, wherein the gaps 838 aresubstantially uniform in size and/or shape.

In the illustrated embodiment, the loop 810 is substantially narrower inwidth than the loop 710 shown in FIG. 8A, thereby increasing theresistance of loop 810 to a value greater than the resistance of loop710. An increase in resistance may allow the loop 810 to be configuredto sense temperature with greater accuracy than the loop 710.

FIG. 8C is an enlarged view of a portion of the soot sensor of FIG. 7according to another embodiment consistent with the present disclosure.In the illustrated embodiment, a plurality of gaps 840, 842 are definedwithin and between each of the first and second subsets of plurality ofundulations 834, 836, wherein the gaps 840, 842 vary in size and/orshape. For example, gap 840 has a width W₁ and gap 842 has a width W₂,wherein width W₁ is generally greater than width W₂. The gaps 840, 842of varying size and/or shape may allow the sensor element 708 to have awider dynamic range of response when sensing soot particle accumulation.

FIG. 9 is perspective view of a soot sensor tip consistent with thepresent disclosure and FIG. 10 is an enlarged perspective sectional viewof the soot sensor tip of FIG. 9 taken along line 10-10. The tip 900 isconfigured to at least partially enclose a soot sensor 1014, wherein thesoot sensor 1014 may include embodiments consistent with the presentdisclosure. The tip 900 includes a body 902 having an exterior surface904 and an interior surface 1004 and a proximal end 908 and a distal end910. In the illustrated embodiment, the body 902 gradually transitionsfrom a generally round shape at the proximal end 908 to a generallyrectangular shape at the distal end 910. The geometry of the body 902 isconfigured to minimize volume on the interior of the tip 900. The body902 defines at least one angularly disposed channel 912 defining a path1016 from the exterior surface 904 of the body 902 to the interiorsurface 1006 of the body 902.

The path 1016 is configured to direct exhaust gas flow to the sootsensor 1014, and may be defined by sidewalls oriented at an angle θ ofless than 90 degrees relative to the first surface 1018 of the sootsensor 1014, as indicated by the arrow A in FIG. 10. The path 1016 maythus be configured at an angle less than 90 degrees relative to thefirst surface 1018 to allow soot from exhaust gas flow to enter theinterior of the body and impact the soot sensor 1014 at an angle lessthan 90 degrees relative to the first surface 1018 of the soot sensor1014. The body 902 may define a plurality of angularly disposed channels912 positioned along an entire circumference of the body.

FIG. 11 is a block diagram of one exemplary embodiment of a soot sensorsystem consistent with the present disclosure. The soot sensor system1100 includes a soot sensor 400. For purposes of clarity anddescription, references will be made to the soot sensor 400 of FIG. 4.It should be noted, however, that the soot sensor system 1100 mayinclude other embodiments of the soot sensor consistent with the presentdisclosure. The soot sensor system 1100 further includes circuitry 1102electrically coupled to the soot sensor 400 and configured to provideelectrical current to the soot sensor 400. In one embodiment, thecircuitry 1102 may be coupled to the first and second electricalcontacts 414, 416 and 424, 426 of the sensor and heater elements 408,418, respectively, for providing currents I_(sense) and/or I_(heater).

The circuitry 1102 includes a measuring circuit 1104 electricallycoupled and configured to communicate with a controller 1106. Themeasuring circuit is also electrically coupled to the soot sensor 400,e.g. to the first and second electrical contacts 414, 416 of the sensorelement 408 and/or the first and second electrical contacts 424, 426 ofthe heater element 418. The measuring circuit 1104 may be configured toapply a voltage between first and second electrical contacts 414, 416and provide an output to the controller 1106 representative of theresulting value of I_(sense). The controller 1106 may be a known enginecontrol unit (ECU) of an automobile and communication between the sootsensor 440, measuring circuit 1104 and the controller may beaccomplished via a known CAN bus.

The value of the current I_(sense) through the sensor element 408 may beutilized to determine an amount of soot that has been deposited on thesoot sensor 400, which may be further indicative of an amount of soot inan exhaust stream communicating with the sensor 400. As previouslynoted, when soot is deposited between the first and second electricalcontacts 414, 416 the electrical resistance of the conductive pathbetween the contacts 414, 416 changes, which results in a correspondingchange in I_(sense). The value of I_(sense) is representative of theamount of soot that has been deposited on the sensor 400.

The measuring circuit 1104 may also be configured to apply a voltagebetween the first and second electrical contacts 424, 426 of the heaterelement. When the value of I_(sense) reaches a predetermined threshold,the controller 1106 may provide an output to the measuring circuit 1104to cause the measuring circuit to activate the heater element 418 byproviding a current I_(heater) to the heater element 418. Uponactivation of the heater element 418, the heater element 418 may heat toa temperature at which accumulated soot particles are incinerated,thereby clearing soot particles from the soot sensor 400, particularlythe sensor element 408.

Additionally, the circuitry 1102 may be configured to detect opencircuits and/or breaks in the sensor and/or heater elements 408, 418.For example, if the sensor element 408 has a break, the circuit betweenthe contacts 414, 416 of the sensor element will be an open circuit or acircuit with higher-than-normal resistance. Thus, if the currentI_(sense) falls below a predetermined threshold, the controller 1106 mayprovide an output indicating failure in the sensor element.

FIG. 12 is a schematic top view of the soot sensor of FIG. 7 including apassivation layer. In the illustrated embodiment, the soot sensor 700may include a pad portion 1244 defining at least the first 714 andsecond 716 electrical contacts of the sensor element 708 and/or thefirst 724 and second 726 electrical contacts of the heater element 718.The soot sensor 700 may further include a passivation layer 1246disposed on the first surface 704 of the substrate 702 and at least overthe pad portion 1244. The passivation layer 1246 may be configured toinhibit and/or prevent any conduction between the first 714 and second716 electrical contacts of the sensor element 708 and/or between thefirst 724 and second 726 electrical contacts of the heater element 718.Additionally, the passivation layer 1246 may be configured to inhibitand/or prevent the occurrence of high heat. The passivation layer 1246may include non-conductive and/or electrically insulating materials.Materials may include oxides, including, but not limited to, alumina,zirconia, yttria, lanthanum oxide, silica, and/or combinations includingat least one of the foregoing, or any like material capable ofinhibiting electrical communication. Additionally, the passivation layer1246 may include materials configured to provide thermal insulation. Inthe illustrated embodiment, the passivation layer 1246 may include athick film glass.

FIG. 13 is a schematic top view of another embodiment of a soot sensor1300 consistent with the present disclosure and FIG. 14 is an enlargedview of a portion of the soot sensor 1300 of FIG. 13. Generally, thesoot sensor 1300 includes a substrate 1302 defining a first surface1304. A first sensor/heater element 1308 and a second sensor/heaterelement 1318 are formed on the first surface 1304. As described ingreater detail herein, the first and second sensor/heater elements 1308,1318 may each be configured to sense soot accumulation in a similarmanner as the sensor element 408 shown in FIG. 4. Additionally, thefirst and second sensor/heater elements 1308, 1318 may each beconfigured to heat and at least partially remove, e.g. incinerate,accumulated soot, thereby cleaning/regenerating the sensor 1300 forcontinued use.

The first and second sensor/heater elements 1308, 1318 each include atleast one continuous loop of conductive material 1310, 1320,respectively, disposed on the substrate 1302. Similar to the embodimentof FIG. 4, the loops 1310, 1320 may be arranged in a serpentineconfiguration including first and second sets of undulations 1312, 1322,respectively. Referring to FIG. 14, the first and second sets ofundulations 1312, 1322 further define first 1328 and second 1330 subsetsof undulations, respectively. A plurality of gaps 1332 are definedwithin and between each of the first 1328 and second 1330 subsets ofplurality of undulations. As shown, the gaps 1332 may have asubstantially uniform size and/or shape. In the illustrated embodiment,the gaps 1332 may have a width W. The width W of the gaps 1332 may rangefrom 10 microns to 100 microns. In one embodiment, the width W of thegaps 1332 is 20 microns. It should be noted that some of the pluralityof gaps 1332 may vary size and/or shape, thereby allowing thesensor/heater elements 1308, 1318 to have a wider dynamic range ofresponse when sensing soot particle accumulation.

As shown, the first sensor/heater element 1308 includes first 1314 andsecond 1316 electrical contacts at opposite ends of the loop 1310. Thefirst and second electrical contacts 1314, 1316 may be configured forcoupling to circuitry for providing current through the loop 1310.Similarly, the second sensor/heater element 1318 includes first 1324 andsecond 1326 electrical contacts at opposite ends of the loop 1320. Thefirst and second electrical contacts 1324, 1326 may be configured forcoupling to circuitry for providing current through the loop 1320.

The first and second sensor/heater elements 1308, 1318 may includeelectrically conductive materials or metals, such as, alumina, gold,platinum, osmium, rhodium, iridium, ruthenium, aluminum, titanium,zirconium, and the like, as well as, oxides, alloys, and combinationsincluding at least one of the foregoing metals. In one embodiment, theelements 1308, 1318 may include alumina having a film platinum tracedeposited on a portion thereof.

The substrate 1302 may include a non-conductive and/or electricallyinsulating materials. Materials may include oxides, including, but notlimited to, alumina, zirconia, yttria, lanthanum oxide, silica, and/orcombinations including at least one of the foregoing, or any likematerial capable of inhibiting electrical communication and providingstructural integrity and/or physical protection. Additionally, the sootsensor 1300 may include thick film and/or thin film constructions.

As described in greater detail herein, the soot sensor 1300 may beconfigured to operate in a first mode (hereinafter referred to as “sootsensing mode”), wherein the first and second sensor/heater elements1308, 1318 are configured to sense soot accumulation on at least thefirst surface 1304 of the soot sensor 1300. The soot sensor 1300 may befurther configured to operate in a second mode (hereinafter referred toas “regeneration mode”), wherein the first and second sensor/heaterelements 1308, 1318 are configured to heat and remove (e.g. incinerate)at least a portion of accumulated soot on the first surface 1304,thereby cleaning/regenerating the sensor 1300.

The first and second sensor/heater elements 1308, 1318 may be configuredto operate separately and independently from one another, as describedin regards to the embodiment of FIG. 4. Additionally, the soot sensor1300 may further include a switch S1 coupled to the second electricalcontacts 1316, 1326 of the first and second sensor/heater elements 1308,1318, respectively, for selectively coupling and decoupling the contacts1316, 1326. For example, when the switch S1 is open, the first andsecond sensor/heater elements 1308, 1318 may operate separately from oneanother. When the switch S1 is closed, the first and secondsensor/heater elements 1308, 1318 may be electrically coupled to oneanother, establishing a continuous loop of conductive material betweencontacts 1314 and 1324.

When the sensor 1300 is in the soot sensing mode, as shown in FIG. 15,an input current I_(sense) may be provided at the first electricalcontact 1314 (or second electrical 1316 contact). The value of I_(sense)may be representative of the amount of soot disposed on the sensor 1300.As shown in FIG. 15, when the switch S1 is closed, the first and secondsensor/heater elements 1308, 1310 are electrically coupled to oneanother and establish a continuous loop of conductive material betweencontacts 1314 and 1324. The current I_(sense) may then pass through boththe first sensor/heater element 1308 and second sensor/heater element1318 to allow both the first and second sensor/heater elements 1308,1318 to act as a single sensor element. Soot particles 1333 are shown asaccumulated on the first surface 1304 of the substrate 1302, includingon the first and second sensor/heater elements 1308, 1318. As soot 1333builds up on the sensor/heater elements 1308, 1318, the resistance ofthe continuous loop (e.g. made of loops 1310 and 1320) changes, whichchanges the value of I_(sense). The value of I_(sense) is thusrepresentative of the amount of soot accumulated on the sensor.

When a threshold amount of soot 1333 accumulates on the first and secondsensor/heater elements 1308, 1318, e.g. as determined by reaching athreshold value of I_(sense), the soot sensor 1300 may be configured toenter the regeneration mode, as shown in FIGS. 16 and 17A-17B. As shownin FIG. 16, when the sensor 1300 is in the regeneration mode, an inputcurrent I_(heater1) may be provided at the first electrical contact 1314(or second electrical 1316 contact) of the first sensor/heater element1308. Similarly, an input current I_(heater2) may be provided at thefirst electrical contact 1324 (or second electrical 1326 contact) of thesecond sensor/heater element 1318. In one embodiment, when a thresholdamount of soot 1333 accumulates on the first and second sensor/heaterelements 1308, 1318, e.g. as determined by reaching a threshold value ofI_(sense), the heater currents I_(heater1) and/or I_(heater2) may beapplied to cause the corresponding first and second sensor/heaterelements 1308, 1318 to heat and at least partially remove, e.g.incinerate, the soot 433, thereby cleaning/regenerating the sensor 1300for continued use.

In one embodiment, when the switch S1 is open, the first and secondsensor/heater elements 1308, 1318 may operate independently of oneanother, wherein the heater current I_(heater1) may be applied to causeonly the first sensor/heater element 1308 to heat up. Similarly, theheater current I_(heater2) may be applied to cause only the secondsensor/heater element 1318 to heat up. When the switch S1 is closed,loops 1310 and 1320 are electrically coupled to one another establishinga single continuous loop of conductive material between the contacts1314 and 1324. The current I_(heater1) may then pass through both thefirst sensor/heater element 1308 and second sensor/heater element 1318to allow both elements 1308, 1318 to act as a single heater element andheat up.

The soot sensor 1300 may be configured to operate in a firstregeneration mode and a second regeneration mode, as shown in FIGS.17A-17D. FIG. 17A illustrates the soot sensor 1300 in a first generationmode and 17B illustrates a schematic view of the circuitry associatedwith the soot sensor 1300 in the first generation mode. As shown, whenin a first regeneration mode, the first and second sensor/heaterelements 1308, 1318 may be arranged in parallel with one another. Thisconfiguration may be suitable for situations in which the first andsecond sensor/heater elements 1308, 1318 are hot and the resistance ishigh, thereby necessitating a need to pass more input current into theelements 1308, 1318 to increase heating of the elements 1308, 1318during high flow conditions.

FIG. 17C illustrates the soot sensor 1300 in a second generation modeand 17D illustrates a schematic view of the circuitry associated withthe soot sensor 1300 in the second generation mode. As shown, when in asecond regeneration mode, the first and second sensor/heater elements1308, 1318 may be arranged in series with one another. Arrangement ofthe first and second sensor/heater elements 1308, 1318 in a seriesgenerally results in a higher resistance than the resistance of aparallel arrangement (shown in FIG. 17A). Thus, operating in the secondregeneration mode (e.g. series configuration) may be suitable forsituations in which it is desirable to limit current consumption and/orwhen the first and second sensor/heater elements 1308, 1318 are cold andrapid heating is desired. Additionally, a higher resistance may alsoprovide an improved temperature measurement of the elements 1308, 1318during regeneration due to higher resolution. It should be noted thatthe first and second regeneration modes may be controlled under solidstate switching and software control. Accordingly, in some embodimentsconsistent with the present disclosure, the soot sensor may beconfigured to provide staged heating, wherein operation of the elements1308, 1318 in the first and/or second regeneration modes may becontrolled (e.g. start, stop, pause, change between modes, etc.) inreal-time or near real-time to account for exhaust flow velocity and/orexhaust temperature.

FIG. 18 is a perspective sectional view of one embodiment of a sootsensor assembly 1800 consistent with the present disclosure. Generally,the soot sensor assembly 1800 includes a housing 1802 having a first end1804 and a second 1806. The housing 1802 is shaped and/or sized topartially enclose a slug insert 1810. The housing 1802 may include metaland/or non-metal material. As shown, the second end 1806 of the housing1802 is shaped and/or sized to receive a portion of the slug insert 1810and retain the slug insert 1810 by way of a ring 1808 coupled to atleast a portion of the slug insert 1810. The ring 1808 may be coupled tothe housing 1802 by various methods known to those skilled in the art.In one embodiment, the ring 1808 may be laser welded to the housing1802, thereby providing a hermetic seal between the housing 1802 andring 1808 (e.g. substantially impervious to air and/or gas).

The soot sensor assembly 1800 further includes a soot sensor 1300coupled to the slug insert 1810. For purposes of clarity anddescription, references will be made to the soot sensor 1300 of FIG. 13.It should be noted, however, that the soot sensor assembly 1800 mayinclude other embodiments of a soot sensor consistent with the presentdisclosure. The soot sensor assembly 1800 further includes a sensor tip1812 coupled to at least the housing 1802 and configured to at leastpartially enclose the soot sensor 1300. The sensor tip 1812 includes abody 1814 having an open proximal end 1816 and a closed distal end 1818.The body 1814 includes an exterior surface 1819A and an interior surface1819B.

In the illustrated embodiment, the proximal end 1816 of the sensor tip1812 may define a flange portion 1820 configured to engagingly mate witha flange portion 1822 of the second end 1806 of the housing 1802. Thesensor tip 1812 may be coupled to at least the housing 1802 at therespective flange portions 1820, 1822, wherein the flange portions 1820,1822 may be sealed to one another. Additionally, the housing 1802 may beconfigured to partially enclose circuitry 1102 electrically coupled tothe soot sensor 1300 and configured to provide electrical current to thesoot sensor 1300.

FIGS. 19A-19B are perspective views of the slug insert 1810 of the sootsensor assembly 1800 of FIG. 18. FIG. 19A illustrates the slug insert1810 separated from the ring 1808 and FIG. 19B illustrates the sluginsert 1810 coupled to the ring 1808. The ring 1808 may include a body1924 defining an interior surface 1928 and a periphery 1926 having acircumference. The ring 1808 may be configured to receive at least aportion of the slug insert 1810. The ring 1808 may include metal and/ornon-metal materials.

In the illustrated embodiment, the slug insert 1810 includes a body 1930having a proximal end 1932 and a distal end 1934. The body 1930 alsoincludes a discrete portion 1936 having a circumference less than thecircumference of the periphery 1926 of the ring 1808, such that thediscrete portion 1930 is configured to fit within the ring 1808 and becoupled to the interior surface 1928. The discrete portion 1936 of theslug insert 1810 may be coupled to the interior surface 1928 of the ring1808 by various methods known to those skilled in the art. In oneembodiment, for example, the discrete portion 1936 of the slug insert1810 may be joined to the interior surface 1928 of the ring 1808 by abrazing method, thereby providing a substantially hermetic seal betweenthe slug insert 1810 and the ring 1808.

The body 1930 of the slug insert 1810 also includes a first surface 1938configured to support at least a portion of the soot sensor 1300 and asecond surface 1940 configured to support electrical connections, e.g.interconnect wires 1946 coupled to leads 1944, as indicated by arrow1947, of the soot sensor 1300. The body 1930 further includes apertures1942 passing from at least the second surface 1940 through the body 1930and to the proximal end 1932 of the slug insert 1810. The apertures 1942are configured to receive and to allow the interconnect wires 1946 topass from circuitry 1102 in the housing 1802 through a portion of theslug insert 1810 (e.g. body 1930) to the second surface 1940.

The first surface 1938 may define a channel shaped and/or sized toreceive at least a portion of the soot sensor 1300. The first surface1938 may further be configured to provide minimal contact with the sootsensor and to prevent heat loss during soot sensor regeneration process(heating of heater element(s)). The sensor element 1300 may be sealed tothe first surface 1938 with glass, thereby increasing durability of thesoot sensor 1300 during production assembly and decreasing vibrationtendency. As appreciated by one skilled in the art, the soot sensor 1300may be coupled to the first surface 1938 by other known methods.

As shown, the second surface 1940 may define a channel shaped and/orsized to receive a portion of the lead wires 1944 and associatedinterconnect wires 1946 coupled thereto. The apertures 1942 havinginterconnect wires 1946 passing therethrough may be filled with asealant, such as glass, thereby providing a hermetic seal between theinterconnect wires 1946 and the associated apertures 1942.

The slug insert 1810 may include non-conductive and/or electricallyinsulating materials. Materials may include oxides, including, but notlimited to, alumina, zirconia, yttria, lanthanum oxide, silica, and/orcombinations including at least one of the foregoing, or any likematerial capable of inhibiting electrical communication. In theillustrated embodiment, the slug insert 1810 may include a ceramicmaterial.

FIG. 19C is an enlarged perspective view of a portion of the soot sensorassembly 1800 of FIG. 18. As described earlier, the soot sensor assembly1800 may include a sensor tip 1812 coupled to at least the housing 1802and configured to at least partially enclose the soot sensor 1300. Inthe illustrated embodiment, the body 1814 of the sensor tip defines atleast one angularly disposed channel 1948 defining a path 1950 from theexterior surface 1819A of the body 1814 to the interior surface 1819B ofthe body 1814. Similar to the embodiment of FIG. 9, the path 1950 isconfigured to direct exhaust flow to the soot sensor 1300. In theillustrated embodiment, the body 1814 of the sensor tip 1812 defines aplurality of angularly disposed channels 1948 positioned along an entirecircumference of the body 1814. It should be noted that the soot sensorassembly 1800 may include other embodiments of a sensor tip consistentwith the present disclosure.

In the illustrated embodiment, the proximal end 1816 of the sensor tip1812 may define a flange portion 1820. The flange portion 1820 isconfigured to engagingly mate with the flange portion 1822 of the secondend 1806 of the housing 1802. The flange portion 1820 of the sensor tip1812 may be laser beam welded to the flange portion 1822 of the housing1802, thereby providing a hermetic seal, as indicated by arrow 1952. Asone skilled in the art would readily appreciate, the flange portions1820, 1822 may be coupled to one another by other known methods.

FIG. 20 is a perspective exploded view of another soot sensor assembly2000 consistent with the present disclosure and FIG. 21 is a perspectiveview of the soot sensor assembly 2000 of FIG. 20 in an assembled state.Generally, the soot sensor assembly 2000 includes an insulating member2002 configured to receive and retain a portion of a soot sensor. Forpurposes of clarity and description, references will be made to the sootsensor 1300 of FIG. 13. It should be noted, however, that the sootsensor assembly 2000 may include other embodiments of a soot sensorconsistent with the present disclosure. The insulating member 2002 mayinclude non-conductive and/or electrically insulating materials.Materials may include oxides, including, but not limited to, alumina,zirconia, yttria, lanthanum oxide, silica, and/or combinations includingat least one of the foregoing, or any like material capable ofinhibiting electrical communication and/or withstanding relatively hightemperatures (e.g., 600° C.). In the illustrated embodiment, theinsulating member 2002 may include a ceramic material.

As shown, the assembly 2000 further includes an inner housing member2004 having a first end 2006 and a second end 2008 and a longitudinallydisposed passageway 2010 extending from the first end 2006 to the secondend 2008. The passageway 2010 is shaped and/or sized to receive aportion of the insulating member 2002 within. As described in greaterdetail herein, the inner housing member 2004 may be shaped and/or sizedto receive one or more materials configured to secure lead wires (shownin FIGS. 22A-22B) in a relatively fixed position.

As shown, the soot sensor assembly 2000 further includes a sensor tipconfigured to be coupled to a portion of the inner housing member 2004.For purposes of clarity and description, references will be made to thesensor tip 1812 of FIG. 18. It should be noted, however, that the sootsensor assembly 2000 may include other embodiments of a sensor tipconsistent with the present disclosure. The sensor tip 1812 may becoupled to at least the inner housing member 2004 and is configured topartially enclose the soot sensor 1300. In the illustrated embodiment,the flange portion 1820 of the sensor tip 1812 is configured toengagingly mate with a flange portion 2012 defined on the second end2008 of the inner housing member 2004. The sensor tip 1812 may becoupled to at least the inner housing member 2004 at the respectiveflange portions 1820, 2012, wherein the flange portions 1820, 2012 maybe sealed to one another.

The assembly 2000 further includes a first spacing member 2014positioned adjacent the first end 2006 of the inner housing member 2002.The size (e.g. width) of the first spacing member 2014 may depend on thedesired length of the lead wires, for example. The soot sensor assembly2000 further includes a second spacing member 2016 positioned adjacentthe spacing member 2016. For purposes of clarity, the second spacingmember 2016 is illustrated partly in section. The size (e.g. width) ofthe second spacing member 2016 may depend on the desired length of theterminals 2018, for example. The first and second spacing members 2014,2016 may include non-conductive and/or electrically insulatingmaterials. Materials may include oxides, including, but not limited to,alumina, zirconia, yttria, lanthanum oxide, silica, and/or combinationsincluding at least one of the foregoing, or any like material capable ofinhibiting electrical communication. In the illustrated embodiment, thefirst and/or second spacing members 2014, 2016 may include a ceramicmaterial.

The soot sensor assembly 2000 further includes a strain relief nugget2020 configured to receive and retain a portion of each of the terminals2018 therein. The nugget 2020 may further be coupled to a wire harnessassembly 2136 (shown in FIG. 21). As shown, the nugget 2020 may includeone or more passageways for each terminal 2018 to be received within.The nugget 2020 may include two complementary halves, wherein, whenpositioned adjacent and complementary to one another, they combine toform a unitary nugget 2020, as shown. The nugget 2020 may furtherinclude a radial groove 2022 defined on a portion thereof. The groove2022 may provide a clearance (e.g. space) to allow a portion of theouter housing member 2026 to be crimped inwardly towards the nugget 2020such that the crimped portion of outer housing member 2026 applieslittle or no force upon the nugget 2020.

The nugget 2020 may be configured to provide strain relief forconnections (e.g. welds) coupling the wires of the wire harness assembly2136 to the terminals 2018. For example, the nugget 2020 may providestrain relief if the wire harness assembly 2136 is pulled duringinstallation or regular use. The nugget 2020 may include non-conductiveand/or electrically insulating materials. Additionally, the nugget 2020may include plastic over-molded material.

As shown, a grommet 2024 may be positioned adjacent the nugget 2020. Thegrommet 2024 may have a hollow tubular cross-section, such that the wireharness assembly 2136 may pass through the grommet 2024 and be coupledto the terminals 2018. The grommet 2024 may include a flexible andresilient material, such as a molded high temperature rubber.

The soot sensor assembly 2000 further includes an outer housing member2026 having a first end 2028 and a second 2030 and a longitudinallydisposed passageway 2032 extending from the first end 2028 to the secondend 2030. The passageway 2032 is shaped and/or sized to receive andenclose the first and second spacing members 2014, 2016, the terminals2018 and respective connections with lead wires from the sensor 1300(shown in FIGS. 22A-22B), the nugget 2020, and a portion of the grommet2024 within. The outer housing member 2026 may include one or morematerials capable of inhibiting electrical communication and providingstructural integrity and/or physical protection to components therein.The outer housing member 2026 may also include material capable ofwithstanding high temperatures.

In the illustrated embodiment, the second end 230 of the outer housingmember 2026 defines a flange portion 2034. The flange portion 2034 isconfigured to engagingly mate with the flange portion 2012 of the secondend 2008 of the inner housing member 2004. As such, the outer housingmember 2026 may be coupled to at least the inner housing member 2004 atthe respective flange portions 2034, 2012, wherein the flange portions2034, 2012 may be sealed to one another by any known methods to providea generally tight seal, thereby preventing moisture and/or othercontaminants from entering the passageway 2032 of the outer housingmember 2026 via the second end 2030.

When the outer housing member 2026 is positioned (e.g. slid) overcomponents of the assembly 2000, a portion of the outer housing member2026 at or near first end 2028 may be crimped, such that a diameter ofthe outer housing member 2026 may be reduced at or near the first end2028. The crimped portion 2138 may compress a portion of the grommet2024 positioned within the passageway 2032, wherein the compressedportion of the grommet 2024 may provide a generally tight seal andprevent moisture and/or other contaminants from entering the first end2028 of the outer housing member 2026. The crimped portion 2138 mayfurther securely retain and fix the nugget 2020 within the passageway2032 of the outer housing member 2028.

FIG. 22A is a top sectional view of the soot sensor assembly of FIG. 21taken along lines A-A and FIG. 22B is a side sectional view of the sootsensor assembly of FIG. 21 taken along lines B-B. As shown, a portion ofthe soot sensor 1300 is positioned and retained within the insulatingmember 2002. In the illustrated embodiment, lead wires 2240 coupled tothe sensor 1300 (e.g. coupled to the first 1314, 1323 and second 1324,1326 electrical contacts of the elements 1308, 1318) extend away fromthe sensor 1300 and into the passageway 2010 of the inner housing member2004 and eventually into the passageway 2032 of the outer housing member2026. The lead wires 2240 may be coupled to associated terminals 2018,as indicated by arrow 2242.

A portion of the lead wires 2240 may be secured in a relatively fixedposition within the inner housing member 2004 by way of a fixingmaterial 2244. In one embodiment, the fixing material 2244 may bedisposed within a portion of the passageway 2010 of the inner housingmember 2004 and completely surround a portion of the lead wires 2240.The fixing material 2244 may be provided in a liquid form and thencured. The fixing material 2244 may be configured to provide stabilityand vibration protection to the sensor 1300 and lead wires 2240, therebyimproving thermal response. The fixing material 2244 may includenon-conductive and/or electrically insulating material, as well asmoisture and/or corrosive resistant material, such as thermosettingplastics.

In one embodiment, the fixing material 2244 may include glass and may beused to seal a portion of the lead wires 2240 and the sensor 1300 withina portion of the passageway 2010 of the inner housing member 2004,thereby increasing durability of the soot sensor 1300 and/or lead wires2240 during production assembly and decreasing vibration tendency. Asappreciated by one skilled in the art, a portion of the lead wires 2240may be fixed and sealed within the inner housing member 2004 by otherknown methods, such as, for example, any known potting methods.

Turning to FIGS. 23A-23B, perspective and sectional views, respectively,of one embodiment of the inner housing member 2304 of the soot sensorassembly 2000 of FIG. 20 are generally illustrated. This embodiment issimilar to the embodiment of FIG. 20, and like components have beenassigned like reference numerals in the twenty-three hundreds ratherthan the two thousands. Generally, the inner housing member 2304includes a first end 2306 and a second end 2308 and a longitudinallydisposed passageway 2310 extending from the first end 2306 to the secondend 2308. The second end 2308 defines a flange member 2312 configured tomatingly engage a flange portion 1820 of the sensor tip 1812. The innerhousing member 2304 further includes an expanded portion 2314 definedalong a radius of the inner housing member 2304. As shown in FIG. 23B,the expanded portion 2314 results in a complementary recessed portion2316 formed on an inner surface 2318 of the passageway 2310.

As previously described, a fixation material 2244, such as glass, forexample, may be filled within a portion of the passageway 2310 tosecurely fix one or more lead wires 2240 within. The fixing material2244 may fill the recessed portion 2316 within the passageway 2310. Whenthe fixing material 2244 has cured, the recessed portion 2316 mayprovide a means of securing the cured fixing material 2244 within thepassageway 2310. More specifically, the cured portion of the fixingmaterial 2244 within the recessed portion 2316 will prevent substantialmovement of the cured fixing material 2244 in at least a longitudinaldirection (i.e. from the first to the second ends 2306, 2308 of theinner housing member 2304). Additionally, the interior surface 2318 ofthe passageway 2310 may be configured to improve interaction between thefixation material 2244 and the inner housing member 2304. For example,in one embodiment, the interior surface 2318 may be roughened by anyknow means (e.g., but not limited to, oxidized, etc.) so as to providean improved interaction between the fixation material 2244 and theinterior surface 2318.

FIGS. 24A-24B are perspective and sectional views, respectively, ofanother embodiment of the inner housing member 2404 of the soot sensorassembly 2000 of FIG. 20. Generally, the inner housing member 2404includes a first end 2406 and a second end 2408 and a longitudinallydisposed passageway 2410 extending from the first end 2406 to the secondend 2408. The second end 2408 defines a flange member 2412 configured tomatingly engage a flange portion 1820 of the sensor tip 1812. The innerhousing member 2404 further includes a recessed portion 2414 definedalong a radius of the inner housing member 2404. As shown in FIG. 24B,the recessed portion 2314 generally results in a complementary generallyannular ridge portion 2416 extending from an inner surface 2418 towardsa center of the passageway 2410.

When the fixing material 2244 is filled within the passageway 2410, thefixing material 2244 may engage and fill around the ridge portion 2416within the passageway 2410. When the fixing material 2244 has cured, theridge portion 2416 may prevent movement of the cured fixing material2244, thereby securing the cured fixing material 2244 within thepassageway 2410. Similar to the embodiment of FIGS. 23A-23B, theinterior surface 2418 of the passageway 2410 may be configured toimprove interaction between the fixation material 2244 and the innerhousing member 2404. For example, in one embodiment, the interiorsurface 2418 may be roughened by any know means (e.g., but not limitedto, oxidized, etc.) so as to provide an improved interaction between thefixation material 2244 and the interior surface 2418.

FIG. 25 is a schematic view of circuitry coupled to the soot sensor ofFIG. 13. The circuitry of FIG. 25 provides a means of nullifying leakagecurrent effects when attempting to enhance soot collection of the sootsensor 1300. As shown, the first and second sensor/heater elements (e.g.Sensor/Heater1 and Sensor/Heater 2) may be configured for coupling tocircuitry 2500 for providing current through the conductive materials ofthe first and second sensor/heater elements, wherein the current may beprovided by a power supply configured to supply an input voltage, forexample, of 38 V. In the illustrated embodiment, the circuitry 2500 mayinclude a first transistor Qs1, a second transistor Qs2, a thirdtransistor Qs3, and a fourth transistor Qs4. The transistors Qs1-Qs4 mayinclude any type of switching device. In the illustrated embodiment, thetransistors Qs1-Qs4 may include MOSFETs. The transistors Qs1-Qs4 may beconfigured to control the application of current from the power supplyto the first and/or second heater elements.

As shown, Qh is off and the third transistor Qs3 is off, therebyproviding the same potential (0V) at the source as the gate throughresistor Rs9. A voltage of 2.5V is applied to the first and secondtransistors Qs1, Qs2, thereby resulting in both the first and secondtransistor Qs1, Qs2 being off. When the first transistor Qs1 off, anvoltage of 5V will be applied to the drain of the second transistor Qs2through the pull-up resistor Rs7. A 2.5V potential is thereby providedat the drain of the third transistor Qs3 and the source of the secondtransistor Qs2 through resistor R5 r. With the circuit arranged asdescribed, the second transistor Qs2 will have a 5V potential at itsdrain and 2.5V at its source, resulting in a drain-source voltage dropof 2.5V. Additionally, with 2.5V at the source and 2.5V at the gate ofthe second transistor Qs2, the second transistor Qs2 will have a 0Vdifference in potential between its gate and its source. The thirdtransistor Qs3 will have a 2.5V potential at its drain, and with itssource being grounded, a potential of 0V at its source, resulting in adrain-source voltage drop of 2.5V, matching that of the secondtransistor Qs2. With the gate and source of the second transistor Qs2being at the same potential as that of the third transistor Qs3, theresulting difference in potential between the third transistors Qs3 gateand source is 0V, again, matching that of the second transistor Qs2.With both the second and third transistors Qs2, Qs3 equally biased, thesoot measurement can be taken with the leakage current effects beingcancelled out.

FIG. 26 is a block diagram of an alternating current (AC) coupled signalprocessing system coupled to the soot sensor of FIG. 13. The AC coupledsignal processing system 2600 may include the soot sensor 1300, as shownin FIG. 13, configured to receive an input AC supply voltage Vac andcoupled to an amplifier 2602 configured to receive signal currentspassing through the soot sensor 1300, including the resistance betweenthe first and second sensor/heater elements 1308, 1318 (Rsoot). Thesystem 2600 may further include a DC restorer 2604 coupled to theamplifier 2602. The DC restorer 2604 may be configured to synchronouslyground signals from said amplifier 2602. A peak detector 2606 may becoupled to and configured to receive signals from the DC restorer 2604.Additionally, a buffer 2608, such as a unity gain operational amplifier(shown in FIG. 20), may be coupled to and configured to receive signalsfrom the peak detector 2606. The system 2600 may further include a lowpass filter 2610 coupled to and configured to receive signals from thebuffer 2608, wherein the low pass filter 2610 may be configured toremove switching transients from received. With the assumption of adynamic resistance of 500 M Ohms to both ground and to the input powersupply, the AC equivalent circuit is illustrated as two 500 M Ohmresistors to ground. Additionally, incrementally, the two 500 M Ohmresistors are coupled between ground and the inverting input of theoperational amplifier 2602, and, as such, may have little effect on anAC signal (current).

FIG. 27 is a schematic view of the circuitry of the signal processingsystem of FIG. 26. To lessen the effect of the DC leakage currents thatmay occur in transistors of the circuitry of the soot sensor 1300, an ACcoupled approach can be implemented. Due to the fact that the dynamicresistance of the DC leakage of the transistors may be much larger thanthe DC resistance, an AC voltage divider would take advantage of thiseffect. The dynamic resistance of an ideal constant current source is ∞Ohms. The dynamic resistance of the leakage of the transistors is δv/δi.In one example, the dynamic resistance may be approximately 500 M Ohms.This value may be more stable with changes in leakage and operatingpoint.

By utilization of the AC coupled signal processing system 2600, the DCleakages of the transistors can be effectively eliminated from theresistance measurement Rsoot. The system 2600 may take advantage of veryhigh dynamic resistance of the sources of leakage currents. For example,the system 2600 takes advantage of being able to couple the square wavestimulation and the resultant AC signals via capacitors, therebyallowing a desired AC signal to pass through the circuitry unattenuated(with properly sized capacitors). The undesired DC voltages (due toleakage currents of the transistors) and/or slow varying voltages due tothermal effects, may be rejected.

Referring to FIG. 27, the soot sensor 1300 may be configured to receivea variety of signal frequencies having varying waveforms (square, sawtooth, sinusoidal, etc) depending on the application taking into accountany software and/or firmware and/or hardware included in the systemand/or sensor. In the illustrated embodiment, the soot sensor 1300 maybe configured to receive a signal having a square waveform havingfrequency of 50 Hz. It should be noted that the optimum frequency mayhelp add robustness to EMC, allow better integration with the softwareand firmware as well as the hardware and might also have effects ofsignal to noise ratio and perhaps add to stability over life.

Additionally, the wave may be balanced around zero volts, such that thewave may cycle equally plus and minus relative to ground. Additionally,a standard waveform may be used that cycles from ground to somepredetermined voltage level, such as 30 Vdc, resulting in a non-balancedwaveform. The non-balanced version may decrease the life of Ptelectrodes due to migration of the Pt. However, the non-balanced may becheaper to implement as far as costs are concerned.

The AC coupled signal processing system 2600 may be configured toeffectively eliminate DC leakages from transistors in the soot sensorcircuitry. During operation, the DC restorer 2604 may be configured tosynchronously ground the signal during the low voltage side of thesquare wave, thereby producing a zero voltage based square wave on theoutput side of the 1.0 uF capacitor. Additionally, the series connectedMOSFET synchronously passes the peak value of this square wave to the1.0 nF capacitor. This capacitor holds this peak value until the nextcycle. This voltage is buffered by a unity gain op-amp 2608 and theoutput is then low pass filtered via the low pass filter 2610 to removeswitching transients. In one example, in which there is no currentleakage, if Rsoot is 100 M, then Vout is 5V*5.0 μA/(3.0 μA+100M)=0.24 V.Similarly, if Rsoot is 5 M, then Vout is 5V*5.0 μA/(5.0 μA+5.0M)=2.5 V.

FIG. 28 is a plot of output voltage vs. resistance associated with anexemplary soot sensor consistent with the present disclosure. Thefollowing table (shown immediately below) includes the measurements ofthe resistance Rsoot between the two heater elements during a sootmeasurement cycle and the corresponding output voltage Vout at 25° C.and 105° C.

Rsoot (M Ohms) Vout (V) at 25° C. Vout (V) at 105° C. 2 4.55 4.55 5 1.841.83 10 0.88 0.88 20 0.44 0.44 50 0.18 0.18 100 0.09 0.09

In the illustrated embodiment, because of the design of the circuitry ofthe AC coupled signal processing system 2600, the output voltage Vout isproportional to 1/Rsoot. This data exhibits a high degree of temperaturestability. The 1/Rsoot method gives high resolution at the lower valuesof Rsoot, where it is desired.

FIG. 29 includes plots of output voltage vs. time associated with anexemplary soot sensor consistent with the present disclosure. Thevoltage (peak to peak) signal used to measure the resistance Rsoot mayaffect the sensor response time. As voltage is increased, response timeis decreased. Since the circuit of the AC coupled signal processingsystem may be configured to operate on a 5 Vdc supply, a charge pump orother means may implemented, thereby increasing sensor excitationvoltage. This may result in the required current from the 5 Vdc supplyto increase.

FIGS. 30A and 30B are schematic views of circuitry associated with anexemplary soot sensor consistent with the present disclosure. FIG. 30Adepicts a pull up resistor configuration and FIG. 30B depicts a pulldown resistor configuration.

FIG. 31 includes plots of resistance vs. time associated with the pullup and pull down resistor configurations of FIGS. 30A-30B. FIG. 31illustrates the resistance of the pull up and pull down resistorconfigurations at two separate excitations voltages, including 10V and5V. In the illustrated embodiment, the pull down resistor configurationcreated a slightly improved sensor response with smoother outputsignals.

FIG. 32 is a plot of supply wattage vs. air flow rate associated with anexemplary soot sensor consistent with the present disclosure exposed toan exhaust gas having a temperature of 200° C. Embodiments of a sootsensor described herein may be configured to operate in a temperaturerange of 0° C. to 650° C., with excursions to 950° C. For example, asoot sensor consistent with the present disclosure may be configured tooperate in an exhaust gas temperate ranging from 150° C. to 650° C. Thewattage required to get the sensor to its regeneration temperaturevaries with exhaust temperature and flow velocity. The wattage ispredictable and repeatable for these different conditions. In theillustrated embodiment, the x-axis illustrates different exhaustvelocities and the y-axis illustrates the required wattage for thesensor to reach its regeneration temperature. The wattage is calculatedby measuring voltage across the first and second heater elements, aswell as any current passing the first and second heater elements.Knowing voltage and current also allows resistance of the heater to becalculated. The resistance vs. temperature curve of the heater is alsoknown. By monitoring the resistance of the heater at regenerationtemperature, it can be determined if the heater resistance has changedor drifted out of its acceptable window.

When the soot sensor is exposed to an exhaust gas stream, certainmaterials present in the exhaust gas may not be completely incineratedby the heater elements during sensor regeneration. These materials mayinclude ash and/or iron oxide, for example. These materials may build upon the surface of the sensor over time and cause a shift in the responsecurve of the sensor (Response curve: the change in sensor resistance vs.mg of soot present on the sensor face). Schemes may be implemented tocounteract the effect of these materials over time. For example, afterdew point is reached, the sensor could be taken through a regenerationcycle and the sensor may store a current resistance in the soot freestate. If this resistance is different than previously seen then theoffset could be used to compensate for the expected sensor responsecurve.

In one aspect, the present disclosure may feature a method of predictingsoot concentration on a soot sensor. The method may include measuringthe time between sensor regenerations and determining the average sootconcentration during that time frame. The time between regenerations canbe less than a couple minutes to over 20 minutes with typical sootconcentration levels. However, with very low soot concentration levels,the time between regeneration cycles can be much longer. The maindisadvantage to this method is that it only provides the average sootconcentration level over a fairly long time period making it slow,especially at low soot concentration levels.

In another aspect, the present disclosure may feature a method ofpredicting soot concentration on a soot sensor. This method may befaster in soot concentration determination than the previous methoddescribed above. The actual response of the sensor (change in sensorresistance vs. time) is used to calculate the mass of soot that ispresent on the sensor in smaller slices of time “real time”. This methoduses the change in resistance vs. time or as measured in change involtage vs. time.

FIGS. 33A-33D are plots of supply voltage vs. time associated with anexemplary soot sensor consistent with the present disclosure. The curvesillustrated in FIGS. 33A-33D are shown with exhaust flow at 15 m/s andexhaust temperature at 270° C. The x-axis is in minutes and the y-axisis percentage of supply voltage. The soot sensor used in each of thecurves is coupled to a pull down resistor (shown in FIG. 30B) on the lowside. The voltage measurement (output signal) is measured across thepull down resistor. As can most clearly be seen in FIGS. 33A-33D, assoot concentration increases, the slope of the sensors also increases.The horizontal blue line indicates the percentage of supply voltage atwhich the sensor gets regenerated. The blue line shown was picked toallow the sensor response to be measured primarily in the linear regionof the sensor response slope. It is possible to further shorten the timespan between sensor regenerations, such as 10% in static states. If thesoot concentration is changing a lot (known by slope changes in thesensor curve) then other percentages could be used. This would result inless soot on the sensor allowing regeneration to occur more quickly.

FIG. 34 is a plot of resistance vs. time associated with an exemplarysoot sensor consistent with the present disclosure. The soot sensor wasexposed to an exhaust gas having a known soot concentration ofapproximately 10.4 mg/m³, a flow rate of approximately 15.5 m/s and atemperature of approximately 273° C. The resistance of the soot sensorwas measured through a full cycle (e.g. sensing of soot accumulationthrough full regeneration of soot sensor). As indicated by arrow A, thesensor resistance begins to drop with soot accumulation. Once apredetermined threshold resistance is reached, as indicated by arrow B,the sensor switches from a soot sense mode to a regeneration mode. Asthe soot is cleaned from the soot sensor, the resistance begins toincrease. As indicated by arrow C, the regeneration mode has ended.

FIG. 35 is a plot of soot accumulation vs. time correlating to the plotof FIG. 34. Generally, FIG. 35 is a linearization of the measurement ofresistance vs. time of FIG. 34. As shown, soot begins to accumulate atapproximately the same time the resistance begins to drop (shown in FIG.34). Similarly, the moment the soot accumulates and reaches apredetermined threshold, as indicated by arrow B, the regeneration modebegins and the soot accumulation level begins to drop (coinciding withthe increase in resistance of FIG. 34). Linearization of the plot ofresistance vs. time into soot accumulation vs. time was determined usingthe formula equation Sensor V out=9206/√R, where Sensor V out is theoutput voltage of the sensor and R is resistance. It should be notedthat this is an exemplary formula equation and other equations may beused for the linearization of the plot of FIG. 34.

FIG. 36 is a plot of sensor response vs. time associated with anexemplary soot sensor consistent with the present disclosure. The sootsensor was exposed to an exhaust gas having a flow rate of approximately27.5 m/s and a temperature of approximately 275° C.

A soot sensor consistent with the present disclosure provide numerousadvantages. The single-layer design of the first and secondsensor/heater elements 1308, 1318 of the soot sensor 1300 of FIG. 13,for example, provides numerous unique and advantageous features. Forexample, the effectiveness of regeneration of the soot sensor isimproved due to the fact that elements may have the ability to bothsense soot accumulation and to heat up to regenerate (i.e. clean) thesubstrate surface. As such, the elements may serve both roles and thereis no need to heat a separate surface, such as the second opposingsurface (e.g. back) of the substrate. Additionally, regeneration in highflow conditions is improved. The second surface (e.g. back) of thesubstrate may be available for additional components, such as anothersensor (e.g. high precision exhaust gas temp sensor, etc.) which furtheradds value and versatility to a system and may reduce costs.

The single layer design also uses less materials, including, but notlimited to, platinum, when compared to some currently known resistive PMsensors. The price of precious metals is relatively high and maycontinue to escalate as it is a finite supply.

A soot sensor circuitry consistent with the present disclosure alsoprovides immediate sensor diagnostics self check upon key and on duringcold start without operating in regeneration mode. The circuitry isrelatively simple and reliable and a diagnostics check may be performedusing low current loop.

Consistent with one embodiment of the present disclosure, there isprovided a soot sensor. The soot sensor includes a substrate defining afirst surface and a second surface opposing the first surface. The sootsensor further includes a first element having at least one continuousloop of conductive material disposed on the first surface of thesubstrate. The at least one element is configured to operate in a firstmode to sense accumulation of soot on at least the first surface of thesubstrate and to operate in a second mode to remove accumulated soot onat least the first surface of the substrate.

Consistent with another embodiment of the present disclosure, there isprovided a soot sensor system. The soot sensor system includes a sootsensor. The soot sensor includes a substrate defining a first surfaceand a second surface opposing the first surface. The soot sensor furtherincludes a first element having at least one continuous loop ofconductive material disposed on the first surface of the substrate. Theat least one element is configured to operate in a first mode to senseaccumulation of soot on at least the first surface of the substrate andto operate in a second mode to remove accumulated soot on at least thefirst surface of the substrate.

The soot sensor system further includes circuitry electrically coupledto the first element. The circuitry is configured to provide electricalcurrent to the first element and to determine an amount of sootaccumulated on the first surface of the substrate and the first elementand to control heating of first element in response to the sootaccumulated on the first surface of the substrate and the first element.

Consistent with yet another embodiment of the present disclosure, thereis provided a method of measuring an amount of soot deposited on a sootsensor. The method includes providing a soot sensor. The soot sensorincludes a substrate defining a first surface and a second surfaceopposing the first surface. The soot sensor further includes a firstelement having at least one continuous loop of conductive materialdisposed on the first surface of the substrate. The at least one elementis configured to operate in a first mode to sense accumulation of sooton at least the first surface of the substrate and to operate in asecond mode to remove accumulated soot on at least the first surface ofthe substrate.

The method further includes monitoring a sense current through the firstelement, the current being representative of an amount of sootaccumulated on the first element. The method further includes providingheater current through the first element in response to the monitoringstep when the sense current reaches a predetermined threshold to therebyremove at least a portion of the soot accumulated on the first element.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified, unless clearly indicated to the contrary.

What is claimed is:
 1. A method of sensing soot in a vehicle soot sensorsystem, the method comprising: providing a soot sensor comprising atleast one trace of conductive material in a continuous loop on a surfaceof a substrate; applying an alternating current (AC) input voltage tothe at least one trace of conductive material to establish an AC sensecurrent through the at least one trace of conductive material; andgenerating, using a peak detector, a peak detector output voltagerepresentative of a peak value of the AC sense current and of an amountof soot accumulated on the soot sensor.
 2. A method according to claim1, the method further comprising amplifying a signal received from theat least one trace of conductive material and applied to the peakdetector to generate an AC output voltage representative of the AC sensecurrent.
 3. A method according to claim 1, the method further comprisinggenerating a synchronously grounded DC restorer output voltage using aDC restorer between the at least one trace of conductive material andthe peak detector.
 4. A method according to claim 1, the method furthercomprising buffering the peak detector output voltage.
 5. A methodaccording to claim 4, wherein buffering comprises buffering the peakdetector output voltage using a unity gain operational amplifier.
 6. Amethod according to claim 1, the method further comprising filtering thepeak detector output voltage using a low pass filter.
 7. A soot sensorsystem comprising: a soot sensor comprising: a substrate, and at leastone trace of conductive material in a continuous loop disposed on thesubstrate; an input voltage source configured to provide an alternatingcurrent (AC) input voltage to the at least one trace of conductivematerial to establish an AC sense current through the at least one traceof conductive material; and a peak detector for providing a peakdetector output voltage representative of a peak value of the AC sensecurrent and of an amount of soot accumulated on the soot sensor.
 8. Asoot sensor according to claim 7, the soot sensor further comprising anamplifier configured to provide an AC output voltage representative theAC sense current.
 9. A soot sensor according to claim 7, the soot sensorfurther comprising a DC restorer coupled between the at least one traceof conductive material and the peak detector and configured to provide asynchronously grounded DC restorer output voltage.
 10. A soot sensoraccording to claim 7, the soot sensor further comprising a buffercoupled to the peak detector output voltage.
 11. A soot sensor accordingto claim 10, wherein the buffer comprises a unity gain operationalamplifier.
 12. A soot sensor according to claim 7, the soot sensorfurther comprising a low pass filter coupled to the peak detector outputvoltage.
 13. A soot sensor system comprising: a soot sensor comprising:a substrate, and at least one trace of conductive material in acontinuous loop disposed on the substrate; an input voltage source forcoupling an alternating current (AC) input voltage to the at least onetrace of conductive material to establish an AC sense current throughthe at least one trace of conductive material; an amplifier configuredto provide an AC output voltage representative of the AC sense current;a DC restorer coupled to the amplifier and configured to synchronouslyground the AC output voltage to provide a DC restorer output voltage;and a peak detector for providing a peak detector output voltagerepresentative of a peak value of the DC restorer output voltage and ofan amount of soot accumulated on the soot sensor.
 14. A soot sensoraccording to claim 13, the soot sensor further comprising a buffercoupled to the peak detector output voltage.
 15. A soot sensor accordingto claim 14, wherein the buffer comprises a unity gain operationalamplifier.
 16. A soot sensor according to claim 13, the soot sensorfurther comprising a low pass filter coupled to the peak detector outputvoltage.